This proposal focuses on the biological functions of glycosylation and glycosidases and much of the work is concerned with the yeast cell wall. We have recently shown that the classical "chitin synthase" of Saccharomyces is not the enzyme involved in budding but that a second enzyme, hitherto undetected, is responsible for bud scar formation. We will investigate biochemical and molecular aspects of this second system. We consider the interesting spatial distribution of chitin in budding yeast to be an intriguing problem in "development". Since starting our exploration of chitin deposition, we have been attracted by other biological aspects of the yeast cell wall. For example, the complex process of mating with its changes in cell shape and cell wall composition, and the timing restraints imposed on cell wall deposition by the cell cycle have suggested numerous biochemical and molecular experiments. Most of the work outlined in this proposal relate directly to these themes.